A nozzle arrangement for an ink jet printhead includes a wafer substrate having a nozzle chamber defined therein. The nozzle arrangement has a nozzle chamber wall that defines an ink ejection port and a rim about the ink ejection port. A series of radially positioned actuators are connected to the wafer...http://www.google.com/patents/US6247790?utm_source=gb-gplus-sharePatent US6247790 - Inverted radial back-curling thermoelastic ink jet printing mechanism

A nozzle arrangement for an ink jet printhead includes a wafer substrate having a nozzle chamber defined therein. The nozzle arrangement has a nozzle chamber wall that defines an ink ejection port and a rim about the ink ejection port. A series of radially positioned actuators are connected to the wafer substrate and extend radially inwardly towards the rim. Each actuator is configured so that a radially inner edge of each actuator is displaceable, with respect to the nozzle rim, into the chamber, upon actuation of the actuator and so that, upon such displacement, a pressure within the nozzle chamber is increased, resulting in the ejection of ink from the ejection port.

Images(16)

Claims(8)

We claim:

1. A nozzle arrangement for an ink jet printhead, the nozzle arrangement comprising:

a wafer substrate having a nozzle chamber defined therein;

a nozzle chamber wall that defines an ink ejection port and a rim about the ink ejection port; and

a series of radially positioned actuators connected to the wafer substrate and extending radially inwardly towards the rim to form a portion of the nozzle chamber wall, each of said actuators being configured so that a radially inner edge of said each of said actuators is displaceable with respect to the nozzle rim into the chamber upon actuation of the actuator and so that, upon such displacement, a pressure within the nozzle chamber is increased, resulting in the ejection of ink from the ejection port.

2. A nozzle arrangement as claimed in claim 1, wherein the actuators are configured to bend into the nozzle chamber away from a center of the nozzle chamber.

3. A nozzle arrangement as claimed in claim 2, wherein each actuator comprises a conductive resistive heating element encased within a material having a coefficient of thermal expansion that is suitable for creating displacement of the actuator upon uneven heating of said material.

4. A nozzle arrangement as claimed in claim 3, wherein the conductive resistive heating element of each actuator is positioned within said material so that uneven heating of said material results, causing the displacement of each actuator into the nozzle chamber.

5. A nozzle arrangement as claimed in claim 3, wherein the resistive heating element of each actuator is serpentine to allow for substantially unhindered expansion of said material.

6. A nozzle arrangement as claimed in claim 3, wherein a number of arms interconnect said rim to said wafer substrate, thereby providing the rim with structural support.

7. An ink jet nozzle arrangement as claimed in claim 1, wherein an ink inlet channel is defined in said wafer substrate and is in fluid communication with the nozzle chamber.

8. A printhead which comprises a plurality of ink jet nozzle arrangements as claimed in claim 1.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application serial numbers (USSN) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.

CROSS-

U.S. Pat. No./

REFERENCED

PATENT APPLICATION

AUSTRALIAN

(CLAIMING RIGHT

PROVISIONAL

OF PRIORITY FROM

PATENT

AUSTRALIAN PROVISIONAL

APPLICATION NO.

APPLICATION)

DOCKET No.

PO7991

09/113,060

ART01

PO8505

09/113,070

ART02

PO7988

09/113,073

ART03

PO9395

09/112,748

ART04

PO8017

09/112,747

ART06

PO8014

09/112,776

ART07

PO8025

09/112,750

ART08

PO8032

09/112,746

ART09

PO7999

09/112,743

ART10

PO7998

09/112,742

ART11

PO8031

09/112,741

ART12

PO8030

09/112,740

ART13

PO7997

09/112,739

ART15

PO7979

09/113,053

ART16

PO8015

09/112,738

ART17

PO7978

09/113,067

ART18

PO7982

09/113,063

ART19

PO7989

09/113,069

ART20

PO8019

09/112,744

ART21

PO7980

09/113,058

ART22

PO8018

09/112,777

ART24

PO7938

09/113,224

ART25

PO8016

09/112,804

ART26

PO8024

09/112,805

ART27

PO7940

09/113,072

ART28

PO7939

09/112,785

AR129

PO8501

09/112,797

ART30

PO8500

09/112,796

ART31

PO7987

09/113,071

ART32

PO8022

09/112,824

ART33

PO8497

09/113,090

ART34

PO8020

09/112,823

ART38

PO8023

09/113,222

ART39

PO8504

09/112,786

ART42

PO8000

09/113,051

ART43

PO7977

09/112,782

ART44

PO7934

09/113,056

ART45

PO7990

09/113,059

ART46

PO8499

09/113,091

ART47

PO8502

09/112,753

ART48

PO7981

09/113,055

ART50

PO7986

09/113,057

ART51

PO7983

09/113,054

ART52

PO8026

09/112,752

ART53

PO8027

09/112,759

ART54

PO8028

09/112,757

ART56

PO9394

09/112,758

ART57

PO9396

09/113,107

ART58

PO9397

09/112,829

ART59

PO9398

09/112,792

ART60

PO9399

6,106,147

ART61

PO9400

09/112,790

ART62

PO9401

09/112,789

ART63

PO9402

09/112,788

ART64

PO9403

09/112,795

ART65

PO9405

09/112,749

ART66

PP0959

09/112,784

ART68

PP1397

09/112,783

ART69

PP2370

09/112,781

DOT01

PP2371

09/113,052

DOT02

PO8003

09/112,834

Fluid01

PO8005

09/113,103

Fluid02

PO9404

09/113,101

Fluid03

PO8066

09/112,751

IJ01

PO8072

09/112,787

IJ02

PO8040

09/112,802

IJ03

PO8071

09/112,803

IJ04

PO8047

09/113,097

IJ05

PO8035

09/113,099

IJ06

PO8044

09/113,084

IJ07

PO8063

09/113,066

IJ08

PO8057

09/112,778

IJ09

PO8056

09/112,779

IJ10

PO8069

09/113,077

IJ11

PO8049

09/113,061

IJ12

PO8036

09/112,818

IJ13

PO8048

09/112,816

IJ14

PO8070

09/112,772

IJ15

PO8067

09/112,819

IJ16

PO8001

09/112,815

IJ17

PO8038

09/113,096

IJ18

PO8033

09/113,068

IJ19

PO8002

09/113,095

IJ20

PO8068

09/112,808

IJ21

PO8062

09/112,809

IJ22

PO8034

09/112,780

IJ23

PO8039

09/113,083

IJ24

PO8041

09/113,121

IJ25

PO8004

09/113,122

IJ26

PO8037

09/112,793

IJ27

PO8043

09/112,794

IJ28

PO8042

09/113,128

IJ29

PO8064

09/113,127

IJ30

PO9389

09/112,756

IJ31

PO9391

09/112,755

IJ32

PP0888

09/112,754

IJ33

PP0891

09/112,811

IJ34

PP0890

09/112,812

IJ35

PP0873

09/112,813

IJ36

PP0993

09/112,814

IJ37

PP0890

09/112,764

IJ38

PP1398

09/112,765

IJ39

PP2592

09/112,767

IJ40

PP2593

09/112,768

IJ41

PP3991

09/112,807

IJ42

PP3987

09/112,806

IJ43

PP3985

09/112,820

IJ44

PP3983

09/112,821

IJ45

PO7935

09/112,822

IJM01

PO7936

09/112,825

IJM02

PO7937

09/112,826

IJM03

PO8061

09/112,827

IJM04

PO8054

09/112,828

IJM05

PO8065

6,071,750

IJM06

PO8055

09/113,108

IJM07

PO8053

09/113,109

IJM08

PO8078

09/113,123

IJM09

PO7933

09/113,114

IJM10

PO7950

09/113,115

IJM11

PO7949

09/113,129

IJM12

PO8060

09/113,124

IJM13

PO8059

09/113,125

IJM14

PO8073

09/113,126

IJM15

PO8076

09/113,119

IJM16

PO8075

09/113,120

IJM17

PO8079

09/113,221

IJM18

PO8050

09/113,116

IJM19

PO8052

09/113,118

IJM20

PO7948

09/113,117

IJM21

PO7951

09/113,113

IJM22

PO8074

09/113,130

IJM23

PO7941

09/113,110

IJM24

PO8077

09/113,112

IJM25

PO8058

09/113,087

IJM26

PO8051

09/113,074

IJM27

PO8045

6,111,754

IJM28

PO7952

09/113,088

IJM29

PO8046

09/112,771

IJM30

PO9390

09/112,769

IJM31

PO9392

09/112,770

IJM32

PP0889

09/112,798

IJM35

PP0887

09/112,801

IJM36

PP0882

09/112,800

IJM37

PP0874

09/112,799

IJM38

PP1396

09/113,098

IJM39

PP3989

09/112,833

IJM40

PP2591

09/112,832

IJM41

PP3990

09/112,831

IJM42

PP3986

09/112,830

IJM43

PP3984

09/112,836

IJM44

PP3982

09/112,835

IJM45

PP0895

09/113,102

IR01

PP0870

09/113,106

IR02

PP0869

09/113,105

IR04

PP0887

09/113,104

IR05

PP0885

09/112,810

IR06

PP0884

09/112,766

IR10

PP0886

09/113,085

IR12

PP0871

09/113,086

IR13

PP0876

09/113,094

IR14

PP0877

09/112,760

IR16

PP0878

09/112,773

IR17

PP0879

09/112,774

IR18

PP0883

09/112,775

IR19

PP0880

09/112,745

IR20

PP0881

09/113,092

IR21

PO8006

6,087,638

MEMS02

PO8007

09/113,093

MEMS03

PO8008

09/113,062

MEMS04

PO8010

6,041,600

MEMS05

PO8011

09/113,082

MEMS06

PO7947

6,067,797

MEMS07

PO7944

09/113,080

MEMS09

PO7946

6,044,646

MEMS10

PO9393

09/113,065

MEMS11

PP0875

09/113,078

MEMS12

PP0894

09/113,075

MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

1. Field of the Invention

The present invention relates to the field of inkjet printing and, in particular, discloses an inverted radial back-curling thermoelastic ink jet printing mechanism.

2. Background of the Invention

Many different types of printing mechanisms have been invented, a large number of which are presently in use. The known forms of printers have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles, has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different forms. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including a step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode form of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclose ink jet printing techniques which rely on the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction and operation, durability and consumables.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there is provided an nozzle arrangement for an ink jet printhead, the arrangement comprising: a nozzle chamber defined in a water substrate for the storage of ink to be ejected; an ink ejection port having a rim formed on one wall of the chamber; and a series of actuators attached to the wafer substrate, and forming a portion of the wall of the nozzle chamber adjacent the rim, the actuator paddles further being actuated in unison so as to eject ink from the nozzle chamber via the ink ejection nozzle.

The actutators can include a surface which bends inwards away from the center of the nozzle chamber upon actuation. The actuators are preferably actuated by means of a thermal actuator device. The thermal actuator device may comprise a conductive resistive heating element encased within a material having a high coefficient of thermal expansion. The element can be serpentine to allow for substantially unhindered expansion of the material. The actuators are preferably arranged radially around the nozzle rim.

The actuators can form a membrane between the nozzle chamber and an external atmosphere of the arrangement and the actuators bend away from the external atmosphere to cause an increase in pressure within the nozzle chamber thereby initiating a consequential ejection of ink from the nozzle chamber. The actuators can bend away from central axis of the nozzle chamber.

The nozzle arrangement can be formed on the wafer substrate utilizing micro-electro mechanical techniques and further can comprise an ink supply channel interconnected to the nozzle chamber. The ink supply channel may be etched through the wafer. The nozzle arrangement may include a series of struts which support the nozzle rim.

The arrangement can be formed adjacent to neighbouring arrangements so as to form a pagewidth printhead.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 4(a) and FIG. 4(b) are again schematic sections illustrating the operational principles of the thermal actuator device;

FIG. 5 is a side perspective view, partly in section, of a single nozzle arrangement constructed in accordance with the preferred embodiments;

FIGS. 6-13 are side perspective views, partly in section, illustrating the manufacturing steps of the preferred embodiments;

FIG. 14 illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of the preferred embodiment;

FIG. 15 provides a legend of the materials indicated in FIG. 16 to 23; and

FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing steps in one form of construction of a nozzle arrangement in accordance with the invention.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, ink is ejected out of a nozzle chamber via an ink ejection port using a series of radially positioned thermal actuator devices that are arranged about the ink ejection port and are activated to pressurize the ink within the nozzle chamber thereby causing the ejection of ink through the ejection port.

Turning now to FIGS. 1, 2 and 3, there is illustrated the basic operational principles of the preferred embodiment. FIG. 1 illustrates a single nozzle arrangement 1 in its quiescent state. The arrangement 1 includes a nozzle chamber 2 which is normally filled with ink so as to form a meniscus 3 in an ink ejection port 4. The nozzle chamber 2 is formed within a wafer 5. The nozzle chamber 2 is supplied with ink via an ink supply channel 6 which is etched through the wafer 5 with a highly isotropic plasma etching system. A suitable etcher can be the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom.

A top of the nozzle arrangement 1 includes a series of radially positioned actuators 8, 9. These actuators comprise a polytetrafluoroethylene (PTFE) layer and an internal serpentine copper core 17. Upon heating of the copper core 17, the surrounding PTFE expands rapidly resulting in a generally downward movement of the actuators 8, 9. Hence, when it is desired to eject ink from the ink ejection port 4, a current is passed through the actuators 8, 9 which results in them bending generally downwards as illustrated in FIG. 2. The downward bending movement of the actuators 8, 9 results in a substantial increase in pressure within the nozzle chamber 2. The increase in pressure in the nozzle chamber 2 results in an expansion of the meniscus 3 as illustrated in FIG. 2.

The actuators 8, 9 are activated only briefly and subsequently deactivated. Consequently, the situation is as illustrated in FIG. 3 with the actuators 8, 9 returning to their original positions. This results in a general inflow of ink back into the nozzle chamber 2 and a necking and breaking of the meniscus 3 resulting in the ejection of a drop 12. The necking and breaking of the meniscus 3 is a consequence of the forward momentum of the ink associated with drop 12 and the backward pressure experienced as a result of the return of the actuators 8, 9 to their original positions. The return of the actuators 8,9 also results in a general inflow of ink 6 from the channel 6 as a result of surface tension effects and, eventually, the state returns to the quiescent position as illustrated in FIG. 1.

FIGS. 4(a) and 4(b) illustrate the principle of operation of the thermal actuator. The thermal actuator is preferably constructed from a material 14 having a high coefficient of thermal expansion. Embedded within the material 14 are a series of heater elements 15 which can be a series of conductive elements designed to carry a current. The conductive elements 15 are heated by passing a current through the elements 15 with the heating resulting in a general increase in temperature in the area around the heating elements 15. The position of the elements 15 is such that uneven heating of the material 14 occurs. The uneven increase in temperature causes a corresponding uneven expansion of the material 14. Hence, as illustrated in FIG. 4(b), the PTFE is bent generally in the direction shown.

In FIG. 5, there is illustrated a side perspective view of one embodiment of a nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber 2 formed with an isotropic surface etch of the wafer 5. The wafer 5 can include a CMOS layer including all the required power and drive circuits. Further, the actuators 8, 9 each have a leaf or petal formation which extends towards a nozzle rim 28 defining the ejection port 4. The normally inner end of each leaf or petal formation is displaceable with respect to the nozzle rim 28. Each activator 8, 9 has an internal copper core 17 defining defining the element 15. The core 17 winds in a serpentine manner to provide for substantially unhindered expansion of the actuators 8, 9. The operation of the actuators 8, 9 is as illustrated in FIG. 4(a) and FIG. 4(b) such that, upon activation, the actuators 8 bend as previously described resulting in a displacement of each petal formation away from the nozzle rim 28 and into the nozzle chamber 2. The ink supply channel 6 can be created via a deep silicon back edge of the wafer 5 utilizing a plasma etcher or the like. The copper or aluminium core 17 can provide a complete circuit. A central arm 18 which can include both metal and PTFE portions provides the main structural support for the actuators 8, 9.

Turning now to FIG. 6 to FIG. 13, one form of manufacture of the nozzle arrangement 1 in accordance with the principles of the preferred embodiment is shown. The nozzle arrangement 1 is preferably manufactured using microelectromechanical (MEMS) techniques and can include the following construction techniques:

As shown initially in FIG. 6, the initial processing starting material is a standard semi-conductor wafer 20 having a complete CMOS level 21 to a first level of metal. The first level of metal includes portions 22 which are utilized for providing power to the thermal actuators 8, 9.

The first step, as illustrated in FIG. 7, is to etch a nozzle region down to the silicon wafer 20 utilizing an appropriate mask.

Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene (PTFE) is deposited and etched so as to define vias 24 for interconnecting multiple levels.

Next, as illustrated in FIG. 9, the second level metal layer is deposited, masked and etched to define a heater structure 25. The heater structure 25 includes via 26 interconnected with a lower aluminium layer.

Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE is deposited and etched to the depth of 1 μm utilizing a nozzle rim mask to define the nozzle rim 28 in addition to ink flow guide rails 29 which generally restrain any wicking along the surface of the PTFE layer. The guide rails 29 surround small thin slots and, as such, surface tension effects are a lot higher around these slots which in turn results in minimal outflow of ink during operation.

Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzle and actuator mask to define a port portion 30 and slots 31 and 32.

Next, as illustrated in FIG. 12, the wafer is crystallographically etched on a <111> plane utilizing a standard crystallographic etchant such as KOH. The etching forms a chamber 32, directly below the port portion 30.

In FIG. 13, the ink supply channel 34 can be etched from the back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of United Kingdom. An array of ink jet nozzles can be formed simultaneously with a portion of an array 36 being illustrated in FIG. 14. A portion of the printhead is formed simultaneously and diced by the ST etch etching process. The array 36 shown provides for four column printing with each separate column attached to a different colour ink supply channel being supplied from the back of the wafer. Bond pads 37 provide for electrical control of the ejection mechanism.

In this manner, large pagewidth printheads can be fabricated so as to provide for a drop-on-demand ink ejection mechanism.

One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double-sided polished wafer 60, complete a 0.5 micron, one poly, 2 metal CMOS process 61. This step is shown in FIG. 16. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 15 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.

2. Etch the CMOS oxide layers down to silicon or second level metal using Mask 1. This mask defines the nozzle cavity and the edge of the chips. This step is shown in FIG. 16.

3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence.

4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 62.

5. Etch the PTFE and CMOS oxide layers to second level metal using Mask 2. This mask defines the contact vias for the heater electrodes. This step is shown in FIG. 17.

6. Deposit and pattern 0.5 microns of gold 63 using a lift-off process using Mask 3. This mask defines the heater pattern. This step is shown in FIG. 18.

7. Deposit 1.5 microns of PTFE 64.

8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim 65 and the rim at the edge 66 of the nozzle chamber. This step is shown in FIG. 19.

9. Etch both layers of PTFE and the thin hydrophilic layer down to silicon using Mask 5. This mask defines a gap 67 at inner edges of the actuators, and the edge of the chips. It also forms the mask for a subsequent crystallographic etch. This step is shown in FIG. 20.

11. Back-etch through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 6. This mask defines the ink inlets 69 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 22.

12. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets 69 at the back of the wafer.

13. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

14. Fill the completed print heads with ink 70 and test them. A filled nozzle is shown in FIG. 23.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.

Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table below under the heading Cross References to Related Applications.

The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.

For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of ink jet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 above which matches the docket numbers in the table under the heading Cross References to Related Applications.

Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry.